Emissions From An Ethanol Fumigated Compression Ignition Engine Engineering Essay

Emissions From An Ethanol Fumigated Compression Ignition Engine Engineering Essay

ABSTRACT. A 4-cylinder Ford 2701C trial engine was used in this survey to research the impact of ethanol fumigation on gaseous and particle emanation concentrations. The fumigation technique delivered vaporised ethyl alcohol into the consumption manifold of the engine, utilizing an injector, a pump and force per unit area regulator, a heat money changer for evaporating ethyl alcohol and a separate fuel armored combat vehicle and lines. With ethanol fumigation, NO and PM2.5 emanations were reduced, whereas CO and HC emanations increased well and particle emanations increased at most test scenes. It was found that ethanol fumigation reduced the extra air factor for the engine and this led to increased emanations of CO and HC, but decreased emanations of NO. PM2.5 emanations were reduced with ethanol fumigation, as ethyl alcohol has a really low “ sooting ” inclination. This is due to the higher hydrogen-to-carbon ratio and besides because ethyl alcohol does non incorporate aromatics, both of which are known soot precursors. The usage of a diesel oxidization accelerator ( as an after-treatment device ) is recommended to accomplish a decrease in the four pollutants that are presently regulated for compaction ignition engines.

KEYWORDS: ethyl alcohol fumigation, compaction ignition engine, gaseous emanations, atom emanations.

Introduction

Globally, the transit sector contributes about 26 % of nursery gas emanations, and due to the turning demand for conveyance ( and therefore increased vehicle kilometers travelled ) , planetary warming extenuation in this sector is turn outing hard [ 1 ] . The usage of bio-fuels ( such as ethyl alcohol and biodiesel ) are presently being explored to cut down exhaust emanations from vehicles [ 2, 3 ] , nevertheless, other factors have an influence on the consumption of bio-fuels, such as the extenuation of planetary heating and energy security issues [ 4, 5 ] . The usage of renewable bio-fuels besides reduces dependance on imported crude oil merchandises, which as a non-renewable energy resource, are being depleted quickly [ 5 ] . Of the bio-fuels available, ethanol is one illustration that is being explored as a replacement for Diesel in the transit sector [ 6 ] .

There are two advantages of ethyl alcohol ( from an emanations position ) that have led to it being pursued as a compaction ignition ( CI ) fuel. First, ethanol provides important full burden atom mass emanation decreases [ 7, 8 ] . Jacobson [ 9 ] showed through simulations that cut downing the black-carbon ( ie carbon black ) emanations from the burning of crude oil dodo fuels is a really effectual scheme for extenuating planetary heating. Additionally, fossil fuel burning is involved in the formation of atmospheric brown clouds, which due to light soaking up by chiefly carbonous aerosol, contribute every bit much to anthropogenetic warming tendencies as nursery gases [ 10 ] . A 2nd advantage of ethyl alcohol is that it offers important life-cycle nursery gas nest eggs [ 11, 12 ] , particularly if waste wood is used as a feedstock for ethanol production. Besides, second-generation bio-fuels that are based on renewable, non-agricultural feedstocks do non interfere with nutrient production, unlike some first coevals feedstocks [ 4 ] .

In this survey, the trial engine was fitted with a fumigation system which delivered ethanol vapor to the consumption manifold of the engine. The fumigation methodological analysis used in this work can be contrasted with the ethyl alcohol intermixing attack, which has received research attending late [ 13, 14 ] . The fumigation attack is capable of presenting more ethyl alcohol on an energy footing ( ~50 % ) than ethyl alcohol blending ( ~25 % ) , which is a major difference between the two engineerings. An added benefit of the fumigation attack is that engine operation can be reverted to pure Diesel operation ( if jobs are encountered with ethanol burning ) since separate fuel armored combat vehicles or systems are used [ 15 ] .

A critical factor act uponing the consumption of ethyl alcohol as a auxiliary fuel for compaction ignition engines is its public presentation from an emanations position. This survey aims to characterize the public presentation of an ethyl alcohol fumigated compaction ignition engine in footings of both its gaseous and atom emanations, with atom figure emanation factors from ethanol fumigation reported for the first clip in this survey. Measurement of atom emanations are set to go more of import in vehicle emanations surveies, since in add-on to a atom mass bound, a atom figure bound for heavy responsibility engines is to be introduced with future European Union criterions [ 16 ] .

Methodology

2.1 ENGINE AND FUEL SPECIFICATIONS

The experimental set-up and design used in this survey follows really closely the description provided in Surawski et al [ 17 ] . The reader is directed to this paper for a more complete description of the engine, trial manners, fuel scenes and trial protocol, which were indistinguishable to those used in the present probe. In the present survey, gaseous and particle figure emanation factors are presented, whereas more elaborate consequences sing the atom physical belongingss ( including the issue of atom size distributions ) and particle chemical science were presented in Surawski et al [ 17 ] . Particle figure emanation factors involve the figure of atoms emitted by the engine per unit of work delivered by the engine ( # /kWh ) , and are hence reported on a brake-specific footing as is done for the other pollutants presented in this paper.

In footings of the experimental design used in this survey, each burden puting involved one ethyl alcohol permutation ( in add-on to the orderly diesel trial at each burden ) , except for half burden operation which employed three ethanol permutations. The experiments were designed this manner as ethanol fumigation is more likely to be implemented under partial burden conditions, instead than at full or light burden [ 15 ] . As a consequence, a more elaborate scrutiny of ethanol fumigation at half burden is undertaken in this survey.

Figure 1 provides an illustration of the experimental set-up employed in this survey. The ethyl alcohol was injected upstream of a heat money changer that was used to evaporate ethanol, as consumption manifolds are non designed to manage two-phase flows. Delivering vaporised ethyl alcohol was a critical demand, since un-vaporised ethyl alcohol would take to an uneven distribution of auxiliary fuel to each cylinder – which is non desirable. After the heat money changer, the injected ethyl alcohol passed through a vortex Godhead [ 18 ] , which consists of a figure of twirling vanes that create a low force per unit area nucleus which exhaustively mixes air with auxiliary fuel before being inducted into each cylinder. The ethanol fumigation system had its ain fuel armored combat vehicle, fuel lines and pump for presenting auxiliary fuel to the engine. In this paper, the term “ EX ” refers to how X % of the entire fuel energy was supplied by ethyl alcohol. At full and intermediate tonss, up to 40 % ethanol permutations ( E40 ) were employed in this survey.

2.2 EMISSIONS MEASUREMENT METHODOLOGY

Gaseous emanations were measured with an Andros 6600/6800 Gas Bench. CO2, NO, CO, HC and O2 emanations were measured straight from the fumes, whereas PM2.5 emanations were sampled from the dilution tunnel utilizing a TSI 8520 Dust-Trak. An iso-kinetic sampling port was used to try PM emanations.

Particle figure distributions were measured with a Scanning Mobility Particle Sizer ( SMPS ) consisting of a TSI 3071A classifier, which pre-selects atoms within a narrow mobility ( and therefore size ) scope, and a TSI 3782 condensation atom counter ( CPC ) which grows atoms ( via condensation ) to optically noticeable sizes. The SMPS package increases the classifier electromotive force in a pre-determined mode so that atoms within a 10-400 nanometer size scope are pre-selected and later counted utilizing the CPC. The package besides integrated the atom figure distribution to enable computation of the entire figure of atoms emitted by the engine ( on a brake-specific footing ) at each trial manner.

A two-stage unwarmed dilution system dwelling of a dilution tunnel ( first ) and an ouster diluter ( 2nd ) was used to thin the fumes gas before particulate size sampling. A 3-way valve was placed on the dilution tunnel to sporadically exchange the fumes flow from the tunnel to after the ouster diluter, enabling either the primary or entire dilution ratio to be computed. In order to cipher dilution ratios, CO2 was used as a tracer gas. CO2 was measured either from the dilution tunnel or after the Dekati diluter ( as indicated in Figure 1 ) , with dilution ratios being calculated utilizing the undermentioned equation:

where was measured with an Andros 6600/6800 Gas Bench ( A± 3 % comparative mistake ) , and and were measured with a Sable Systems CA-10A Carbon Dioxide Analyser ( A± 1 % comparative mistake ) . Laboratory background CO2 measurings were made before the beginning of each trial session. Both CO2 measurings were performed with a sampling frequence of 1 Hz. Velocity and temperature were monitored within the dilution tunnel to guarantee that disruptive conditions were achieved, therefore enabling particulate affair to be to the full assorted before trying occurred.

For internal burning engines, the extra air factor ( I» ) ( or relative air-fuel ratio ) is defined as the ratio of the existent air-fuel ratio to the stoichiometric air-fuel ratio [ 19 ] . The undermentioned chemical equation describes complete burning for a hydrocarbon and ethyl alcohol:

( 1 )

where:

is the figure of moles of ethyl alcohol consumed per mole of Diesel,

and is a co-efficient that makes ( 1 ) balance.

From ( 1 ) , the extra air factor for dual-fuel burning of Diesel and ethyl alcohol can be calculated via:

RESULTS AND DISCUSSION

Engine public presentation informations for the experimental run appears in Table 1 and includes informations on fuel ingestion, extra air factors, brake thermic efficiencies, brake average effectual force per unit areas ( BMEP ) and the count average diameter of the atom emanations for each trial.

Figure 2 nowadayss brake-specific PM2.5 and atom figure emanations. The PM2.5 informations in Figure 2 was antecedently published in [ 17 ] , but has been augmented in this survey by atom figure emanation factors. Error bars present in figures denote A± one standard divergence of the informations collected for each emanations parametric quantity.

Brake-specific atom mass emanations decreased for all ethanol fumigation permutations, except for the E10 trial at idle manner. The most important atom mass decreases were apparent at full burden, where a 40 % ethanol permutation provided a quintuple decrease in atom mass. Particle mass decreases at other tonss were non as significant ; nevertheless, atom mass was reduced by about 50 % at half burden with a 40 % ethanol permutation. Slight atom mass decreases were achieved at one-fourth burden ( ~ 10 % ) , whilst a modest atom mass addition occurred at idle manner ( ~ 55 % ) . The count average diameter of atoms emitted for the E10 idle manner trial ( see Table 1 ) are about 20 % bigger that those for E0 idle. So assumptive spherical atoms with unit denseness, and taking into history that fewer atoms are emitted for the E10 idle trial, a 55 % addition in particle mass could be considered sensible. The atom mass consequences are in qualitative understanding with Heisey and Lestz [ 8 ] who observed that decreases in atom mass increased with increasing engine burden. Full burden atom mass decreases of up to 65 % were achieved in the survey by Heisey and Lestz [ 8 ] ( utilizing a 40 % ethanol permutation ) , whereas Abu-Qudais et Al [ 7 ] reported full burden atom mass decreases in the 33-51 % scope ( utilizing a 20 % ethanol permutation ) . Consequently, the atom mass decreases achieved in this survey ( at full burden ) were greater than those encountered in other fumigation surveies. A possible account for this behavior is that ethyl alcohol was passed through a low force per unit area part in a vortex Godhead. This meant that the auxiliary fuel would hold been mixed more thoroughly ( compared to other fumigation surveies ) before come ining the cylinder. Since fuel-rich parts are known to bring forth increased PM emanations [ 20 ] , a exhaustively assorted charge may hold assisted in stamp downing the formation of particulate affair.

A figure of factors have contributed to the important atom mass decreases achieved at one-fourth, half and full burden with ethanol fumigation. The first observation is that the fumigant ( ethyl alcohol ) has a really low sooting inclination, as it is free from aromatics and has a much lower carbon-to-hydrogen ( C/H ) ratio than Diesel. Both the aromatics content and the C/H ratio of a fuel are indexs of its sooting inclination [ 21 ] . The burning of fumigated ethyl alcohol will besides bring forth more OH groups [ 17 ] , which will help in the oxidization of carbon black, taking to take down PM emanations [ 21 ] . Additionally, the secondary fuel introduced via fumigation is pre-mixed and is hence less likely to organize particulates, go forthing the fuel-rich Diesel spray as the primary beginning of atom mass emanations. Interestingly, the above mentioned factors contribute to take down atom mass emanations even though burning is more fuel-rich with ethanol fumigation ( see Figure 6 ) .

Figure 2 shows that whilst atom mass decreases were observed with ethanol fumigation ( except at idle manner operation ) , atom figure emanations by and large increased. At full burden, the figure of atoms emitted by the engine more than doubled, since the E40 fuel scene produced a nucleation manner which formed a big figure of nanoparticles with a diameter & lt ; 50 nanometer ( see [ 17 ] for size distribution information ) . No such nucleation manner was apparent with orderly Diesel operation at full burden. At half burden, more atoms are emitted for the E10 trial but fewer atoms were emitted for the E20 and E40 trials. At one-fourth burden, the figure of atoms emitted increased by approximately 20 % and decreased by 15 % at the idle manner. Generally, ethanol fumigation increased the figure of atoms emitted by the engine. The addition in atom figure emanations occurred due to the phenomenon of homogenous nucleation ( as outlined in [ 17 ] ) , which in an engine ‘s fumes, is a gas-to-particle transition procedure driven by super-saturated volatile bluess. A decrease in atom mass emanations can worsen the atom figure emanations ( as has occurred in this survey ) , since alternatively of volatile bluess distilling on a atom, they are more likely to stay in the gas stage ( therefore increasing their impregnation ratio ) and become involved in nucleation.

Ethanol fumigation reduced brake-specific NO emanations at all tonss ( see Figure 3 ) with decreases runing from 20 % ( idle manner ) to about 70 % ( half burden ) . Whilst merely No measurings were made in this survey and non NOx ( NO and NO2 ) , comparing NO consequences with NOx consequences is valid for older engines as their NO2/NOx ratio is about 5 % [ 22 ] .

The NO decreases exhibited by this engine were by and large higher than those reported in other fumigation surveies ( which report a NOx lessening ) , although Heisey and Lestz [ 8 ] did describe a 50 % NOx decrease at 2400 revolutions per minute, with a 40 % ( by energy ) ethanol permutation and a 1/3 rack scene. In a rack and pinion system for fuel injection, additive gesture of the rack imparts round gesture to a control arm which varies the shot of the bringing speculator. As a consequence, changing the rack place is correspondent to commanding the burden of an engine.

To cast visible radiation on the NO consequences, a treatment of the drawn-out Zeldovich mechanism is required, which consists of the undermentioned three chemical equations [ 19, 20 ] :

( 2 )

( 3 )

( 4 )

The public presentation informations in Table 1 shows that at each burden scene, ethanol fumigation reduces the extra air factor, doing the burning more fuel rich. The decreased extra air factor implies that less molecular Oxygen ( O2 ) and Nitrogen ( N2 ) is available for burning in fumigation manner. With a decrease in O2 and N2 handiness, equations ( 2-3 ) of the Zeldovich mechanism are less likely to continue, hence restricting the production of NO. Figure 6 shows that the NO emanations at half burden operation are correlated rather good with the extra air factor ( R2=0.97 ) .

Brake-specific CO emanations ( see Figure 4 ) increased at all tonss tested, except idle manner. The thermic efficiency of the engine was somewhat higher under idle manner operation with E10, taking to take down CO and HC emanations. A 40 % ethanol permutation at half burden about tripled CO emanations, whereas the same ethanol permutation at full burden about doubled CO emanations. CO emanations about doubled at one-fourth burden, nevertheless, merely a 20 % ethanol permutation was used in this instance. Idle mode CO emanations were reduced by about 15 % utilizing a 10 % ethanol permutation. At half and one-fourth tonss these consequences were in good understanding qualitatively with Heisey and Lestz [ 8 ] , who observed big additions in CO emanations at the 1/3 and 2/3 rack scenes at 2400 revolutions per minute. These consequences differ from those of Heisey and Lestz [ 8 ] in that big CO additions ( ~ 80 % ) were besides observed at full burden.

Brake-specific HC emanations appear in Figure 5. HC emanations increased at all tonss, as ethanol fumigation increased, except at idle manner and besides for the E20 trial at half burden. The most important HC additions were achieved at half burden, where a 40 % ethanol permutation more than doubled HC emanations. At full burden, the same ethyl alcohol permutation led to a doubling of HC emanations. Idle manner HC emanations were reduced by about 30 % utilizing a 10 % ethanol permutation, whereas HC emanations increased by approximately 30 % at one-fourth burden utilizing a 20 % ethanol permutation. These consequences are in understanding with Jiang et al [ 23 ] , who reported really important HC emanation additions at full burden but more moderate HC additions at lower burden.

The extra air factor ( ) ( or its opposite, the equality ratio ) is an engine parametric quantity that has a strong influence on the composing of Diesel exhaust [ 24 ] . To research this consequence, the CO, HC, NO and PM2.5 emanations at half load half been plotted versus the extra air factor ( see Figure 6 ) . With a higher extra air factor, CO and HC should be more readily oxidised to finish burning merchandises, giving lower CO and HC emanations [ 19 ] . This general tendency is apparent in the dataset, with CO emanations correlating really good ( R2=0.99 ) with the extra air factor, but this correlativity does non execute every bit good for HC emanations ( R2=0.54 ) . The difference in the strength of these two correlativities suggests that factors other than the extra air factor govern HC emanations, such as fire slaking [ 19 ] .

It can be observed that ethanol fumigation leads to instead big additions in both CO and HC emanations. Two chief factors contribute to this. First, a decrease in the extra air factor with ethanol fumigation leads to more fuel-rich burning ( see Figure 6 ) . Second, the fact that auxiliary fuel is inducted during the consumption shot, and non delivered to the burning chamber in a controlled mode ( as would be the instance if ethyl alcohols were injected ) , can take to ethanol encroaching on the cylinder wall and burning chamber. This will take to uncomplete burning ( and accordingly increased CO and HC emanations ) if the Diesel fire is extinguished before making the cylinder and burning chamber wall.

As for the other pollutants, a decrease in extra air factor reduces the handiness of molecular O ( O2 ) and N ( N2 ) which inhibits the formation of NO in the drawn-out Zeldovich mechanism ( R2=0.97 ) . Even though particulate affair emanations are a byproduct of a fuel-rich Diesel spray, PM2.5 emanations are reduced with a lower extra air factor.

Decision

The consequences from this probe showed that PM2.5 and NO emanations ( two major CI engine pollutants ) were significantly reduced by ethanol fumigation. Conversely, HC and CO emanations increased well. To accomplish a decrease in the four pollutants presently regulated, the usage of a diesel oxidization accelerator ( as an after-treatment device ) should be investigated, as it will help in oxidizing hydrocarbons and CO to finish burning merchandises. There was an addition in the figure of atoms emitted at most trial manners, bespeaking that there may be a demand for particulate after-treatment, such as a Diesel particulate filter. Alternatively, the sum of ethyl alcohol that is fumigated at a peculiar burden may necessitate to be limited by the injection control system.

A celebrated restriction of the gaseous emanation measurings is that merely NO consequences are presented. NO2 emanation additions would be expected with ethanol fumigation, as NO2 increases with methanol fumigation [ 25, 26 ] and ethyl alcohol has similar physico-chemical belongingss to methanol. There would besides be a burden dependence for NO2 emanations, with lower tonss bring forthing higher brake-specific NO2 emanations.

ACKNOWLEDGEMENTS. We appreciatively acknowledge contributions of fuel ethyl alcohol from Freedom Fuels and Rocky Point Sugar Refinery. The writers thank Alternative Engine Technologies Pty Ltd for supplying equipment and package enabling the dual-fuel installing on the trial engine. The writers thank the undermentioned undergraduate pupils for ergometer operation during the two experimental runs: Mr Adrian Schmidt, Mr Peter Clark, Mr Yoann Despiau and Mr Steven Herdy. We thank Mr Tony Morris for helping with the design of the experimental runs. We besides thank Mr Jonathan James and Mr Glenn Geary for enabling an undergraduate instruction engine to be used for research intents. Proofreading aid from Mr Timothy Bodisco is greatly appreciated. This work was undertaken under an Australian Research Council Linkage Grant ( LP0775178 ) .